Antonio Margarito vs. Kermit Cintron - 1 - Part 1 of 4

Santos then vacated the WBO title to go up in weight and pursue the WBO Light Middleweight Championship and Margarito was assigned to fight Antonio Díaz for the vacant title in front of an HBO Boxing audience. On March 16, 2002, Margarito crowned himself world champion, beating Diaz by knockout in round ten. He defended that crown with a decision in twelve over Danny Perez Ramírez and a knockout in two over former WBA title holder Andrew Lewis. Lewis was a southpaw and a hard puncher, but had been exposed as having a weak chin, while Margarito proved that he has a world class chin. He publicly asked for a unification bout with then WBC and WBA Champion Ricardo Mayorga.

At this point, Margarito considered going up in weight to try to lure Fernando Vargas, Oscar De La Hoya or Shane Mosley into a lucrative fight, or Santos into a rematch at the light middleweight division. On October 17, 2003, Margarito made his light middleweight division debut with a two round knockout win over Maurice Brantley in Phoenix, Arizona.

On January 31, 2004, back in the welterweight division, he retained his title with a second round knockout of Canada's previously undefeated Hercules Kyvelos.

Margarito faced Daniel Santos in a rematch on September 11 of the same year at the José Miguel Agrelot Coliseum in San Juan for Santos' WBO Light Middleweight title. The rematch also ended because of a headbutt, but this time, as the fight had already reached the four rounds mark needed for fights like these to be decided by judges, Margarito lost by a split ten round technical decision. He was down on two scorecards when the fight was stopped.

On April 23, 2005, Margarito retained his WBO welterweight title against another Puerto Rican, undefeated world class puncher Kermit Cintron, dropping him four times on his way to a fifth round knockout. This was regarded as one of his best wins.

After almost a ten month layoff, Margarito returned to the boxing ring on February 18, 2006, retaining his title with a first round knockout of Jaime Manuel Gomez, who had lasted eleven rounds with Mosley for the IBF Lightweight title eight and a half years before.

On December 2, 2006, Margarito defeated future champion Joshua Clottey by a twelve round unanimous decision. Margarito set a Compubox all-time record of 1675 total punches thrown in a twelve round bout